The present invention relates to a vehicular lighting device, and more particularly to a vehicular lighting device in which desired light distribution characteristics are obtained.
Conventionally, in vehicular lighting devices various configurations and combinations of reflector surfaces and steps formed on the surface of lenses have been employed in order to obtain desired light distribution characteristics.
In some lighting devices, light emitted from a bulb is diffused vertically upward and downward by a reflecting surface, and then horizontally leftward and rightward by a lens. Others are constructed such that the light is diffused horizontally leftward and rightwardly the reflecting surface and then vertically downward and upward by the lens.
In recent years, as automobiles have been designed with lower heights, there has been a tendency and requirement to reduce the vertical dimensions of vehicular lights and to provide them with a thin and compact construction as a whole. This of course requires that the lenses and reflectors also be reduced in their vertical dimensions. Doing so, however, has often resulted in insufficient vertical light diffusion, which in turn results in an undesirable vertically flat light distribution pattern. Accordingly, desired light distribution characteristics cannot be obtained.
Also, a variety of lighting devices have been proposed which are constructed such that the lighting of, for example, front turn signals can be observed from the side-and-rear position of the vehicle. This construction is intended to meet the legal requirements in the United States for the front turn signal lamps to be observable from the side rear of the vehicle at an angle of 45 degrees relative to the longitudinal direction of the vehicle.
FIG. 1 shows another conventional lighting device in which a lens-cut 18 composed of a plurality of elongated projections and recesses is formed on an outer lens 14 in such a manner that the light from the light source is directed not only toward the front of the vehicle but also toward the side rear of the vehicle. As an alternative to the lens-cut 18, a second inner lens (not shown) can be provided between the Outer lens 14 and a globe-like colored inner lens. The second inner lens is formed with a lens-cut thereon for directing the light toward the side rear of the vehicle.
However, the lighting device in which the outer lens 14 is formed with the lens-cut 18 thereon suffered from the problem that the lens-cut 18 can be clearly observed from the outside. That is, the lens-cut 18 does not visually merge well with a step pattern 20, resulting in a poor aesthetic appearance. On the other hand, the lighting device in which the second inner lens is formed with a lens-cut thereon has a higher cost due to the addition of the second inner lens.